A power supply network and a ground network provide power to an integrated circuit. During operation of a digital integrated circuit, switching in the digital logic creates spikes in the current demand from the power supply network and the ground network. These current spikes create power supply fluctuations across the inductance of the power supply network and ground fluctuations across the inductance of the ground network. These fluctuations are commonly known as “simultaneously switching output noise,” or SSO, when they arise from currents circulating specifically through a digital logic output. These fluctuations are also commonly known as “power and ground rail collapse” when they arise due to currents otherwise circulating generally within a digital integrated circuit. The power supply fluctuations and the ground fluctuations effectively reduce the available power supply voltage for the digital logic, potentially causing improper operation of the digital logic. In addition, these current spikes can excite a resonance between a capacitance and an inductance within the power supply network and/or the ground network, further reducing the available power supply voltage within the digital integrated circuit when the resonance accumulates fluctuations from multiple current spikes.
“Decoupling capacitors” that are placed between the power supply network and the ground network provide a low impedance path for the current spikes, and this low impedance path reduces fluctuations and resonance in the power supply and ground networks. However, decoupling capacitors outside the integrated circuit do not prevent fluctuations and resonance in the portion of the power supply and ground networks that is inside the integrated circuit. In addition, decoupling capacitors in the package of the integrated circuit do not prevent fluctuations and resonance in the portion of the power supply and ground network that couples the decoupling capacitors to the digital logic within the integrated circuit.
One or more embodiments of the present invention may address one or more of the above issues.